/****************************************************************************
 * net/bluetooth/iob/iob_contig.c
 *
 *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <string.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <tinyara/bluetooth/iob/iob.h>

#include "iob.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#ifndef MIN
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: iob_contig
 *
 * Description:
 *   Ensure that there is'len' bytes of contiguous space at the beginning
 *   of the I/O buffer chain starting at 'iob'.
 *
 ****************************************************************************/

int iob_contig(FAR struct iob_s *iob, unsigned int len)
{
	FAR struct iob_s *next;
	unsigned int ncopy;

	/* We can't make more contiguous space that the size of one I/O buffer.
	 * If you get this assertion and really need that much contiguous data,
	 * then you will need to increase CONFIG_IOB_BUFSIZE.
	 */

	DEBUGASSERT(len <= CONFIG_IOB_BUFSIZE);

	/* Check if there is already sufficient, contiguous space at the beginning
	 * of the packet
	 */

	if (len <= iob->io_len) {
		/* Yes we are good */

		return 0;
	}

	/* Can we get the required amount of contiguous data by just packing the
	 * head I/0 buffer?
	 */

	else if (len <= iob->io_pktlen) {
		/* Yes.. First eliminate any leading offset */

		if (iob->io_offset > 0) {
			memcpy(iob->io_data, &iob->io_data[iob->io_offset], iob->io_len);
			iob->io_offset = 0;
		}

		/* Then move what we need from the next I/O buffer(s) */

		do {
			/* Get the next I/O buffer in the chain */

			next = iob->io_flink;
			DEBUGASSERT(next != NULL && next->io_len > 0);

			/* Copy what we need or what we can from the next buffer */

			ncopy = len - iob->io_len;
			ncopy = MIN(ncopy, next->io_len);
			memcpy(&iob->io_data[iob->io_len], &next->io_data[next->io_offset], ncopy);

			/* Adjust counts and offsets */

			iob->io_len += ncopy;
			next->io_offset += ncopy;
			next->io_len -= ncopy;

			/* Handle a (improbable) case where we just emptied the second
			 * buffer in the chain.
			 */

			if (next->io_len == 0) {
				iob->io_flink = iob_free(next);
			}
		} while (len > iob->io_len);

		/* This should always succeed because we know that:
		 *
		 *   pktlen >= CONFIG_IOB_BUFSIZE >= len
		 */

		return 0;
	}

	/* Otherwise, the request for contiguous data is larger then the entire
	 * packet.  We can't do that without extending the I/O buffer chain with
	 * garbage (which would probably not be what the caller wants).
	 */

	else {
		ioberr("ERROR: pktlen=%u < requested len=%u\n", iob->io_pktlen, len);
		return -ENOSPC;
	}
}
